Water based rolling lubricant

ABSTRACT

A COOLANT-LUBRICANT FOR THE COLD ROOLING OF ALUMINUM AND OTHER LIGHT METALS COMPRISING AN OIL-IN-WATER EMULSION WHEREIN THE NONAQUEOUS FRACTION OF SAID EMULSION CONSISTS ESSENTIALLY OF FROM ABOUT 45 TO 90% OF A LIGHT PETROLEUM OIL, FROM ABOUT 5 TO 50% BY WEIGHT OF ESTERS OF FATTY ACIDS, FROM ABOUT 5 TO 50% BY WEIGHT OF FATTY ALCOHOLS, BETWEEN ABOUT 0.05 TO 1.0% BY WEIGHT OF AN OIL-SOLUBLE EMULSIFIER AND PREFERABLY BETWEEN ABOUT 0.05 AND 1.0% BY WEIGHT OF AN OIL-INSOLUBLE EMULSIFIER. THE NONAQUEOUS FRACTION OF SAID EMULSION AMOUNTS TO BETWEEN ABOUT 3 AND 20% OF THE TOTAL WEIGHT OF THE EMULSION. PREFERABLY, THE WATER PHASE OF THE EMULSION HAS AN ALKALI METAL SALT CONCENTRATION OF BETWEEN ABOUT 10 AND 400 PARTS PER MILLION AND A PH LEVEL BETWEEN ABOUT 5.0 AND 7.4.

United States Patent 3,726,799 WATER BASED ROLLING LUBRICANT Ewell E.McDole, Danville, and Frank L. Howard, Livermore, Califi, assignors toKaiser Aluminum & Chemical Corporation, Oakland, Calif. No Drawing.Filed May 18, 1971, Ser. No. 144,645 Int. Cl. C10m 1/06, 1/22, 1/46 U.S.Cl. 252-495 29 Claims ABSTRACT OF THE DISCLOSURE A coolant-lubricant forthe cold rolling of aluminum and other light metals comprising anoil-in-water emulsion wherein the nonaqueou's fraction of said emulsionconsists essentially of from about 45 to 90% of a light petroleum oil,from about 5 to 50% by weight of esters of fatty acids, from about 5 to50% by weight of fatty alcohols, between about 0.05 and 1.0% by weightof an oil-soluble emulsifier and preferably between about 0.05 and 1.0%by weight of an oil-insoluble emulsifier. The nonaqueous fraction ofsaid emulsion amounts to between about 3 and 20% of the total weight ofthe emulsion. Preferably, the water phase of the emulsion has an alkalimetal salt concentration of between about and 400 parts per million anda pH level between about 5.0 and 7.4.

BACKGROUND This invention relates to the cold rolling of light metalssuch as aluminum and magnesium. As used herein the terms aluminum,magnesium, and light metals include the pure metals as well as thealloys thereof.

For many years the aluminum and other light metal industries haveattempted to'use oil-in-water emulsions as coolant-lubricants in thecold rolling of sheet metal products. Oil-in-water emulsions provide asubstantial increase in cooling rates over the previously employed oilbase lubricants. The major advantage resulting from the improved coolingrates is an improved mill roll shape control. Attendant with theincreased cooling rates are higher mill speeds and greater reductionsper pass. However, when the prior oil-in-water emulsions Were used thesurface finish of the resultant sheet products was severely impaired.Water stain, brown stain, smut and other surface irregularities renderedthe sheet products undesirable, and for most purposes unacceptable.Water stain, which is a white haze or a splotchy appearance, is causedby the reaction of water with the surface of the workpiece. Brown stainforms during heat treatments after rolling, such as annealing, due tothe thermal decomposition of the oil components which remain on thesheet after rolling. The formation of a dark smut which occurs duringrolling also is due to the thermal decomposition of the organiccomponents. The dark smut and brown stain can be minimized by utilizinglubricity agents with relatively short carbon chains, but this may noteliminate the problem. The brown stain is a permanent discoloration ofthe sheet surface which is diificult to remove. The smut is easilyremoved by wiping with a cloth or the like, but this requires anadditional processing step which is not desired.

A common problem associated with the prior art emulsion and dispersionswas the inability to prevent the buildup of metal and oxide particles onthe roll surface and the embedding of the particles into the surface ofthe workpiece.

If the speed of the mill and/ or the amount of reduction per passexceeds the lubrication properties of the emulsion, the surface of thesheet exhibits an irregularity commonly termed herringbone eifect, whichis caused by failure of the lubricant film, allowing steel-to-aluminumcontact and consequent welding of aluminum to the roll.

The nonaqueous fraction of the prior emulsions usually included a basepetroleum oil, fatty acids, fatty acid esters, fatty oils orcombinations thereof, and various types of emulsifiers. Others, such asMcLean et al. in U.S. 3,505,849, have proposed that an oil-free aqueousdispersion of fatty acids, fatty alcohols, fatty esters, fatty aminesand fatty acid amides, or combinations thereof, be used for coldrolling.

SUMMARY OF INVENTION The oil-in-water emulsion of the present inventionprovides for the substantial improvement in the rolling aluminum andother light metals without the prior art problems of water stain, brownstain, and various other surface imperfections on the resultant sheetproducts. The nonaqueou's or oil fraction of the emulsion comprises fromabout 45 to about by weight of a light petroleum oil, between about 5and 50% by weight of a fatty acid ester, between about 5 and 50% of afatty alcohol and between about 0.05 and 1.0% by weight of asubstantially water-insoluble, oil-soluble emulsifier. Preferably, thenonaqueous fraction also includes between about 0.05% and 1.0% by weightof an oil-insolub1e nonionic emulsifier. The nonaqueous fraction amountsto between about 3 and 20% of the total weight of the emulsion.Substantially improved reductions per pass can be obtained when theaqueous phase of the emulsion contains an alkali metal saltconcentration between about 10 and 400 parts per million. For a stableoil-in-water emulsion during rolling, the pH of the aqueous fraction ismaintained between 5.0 and 7.4.

DESCRIPTION OF THE INVENTION The base oil of the present invention isessentially a paratfinic, isoparaflinic, or naphthenic hydrocarbon oil,or a combination thereof with a viscosity of about 30 to about SSU at100 F., preferably between about 30 and 70 SSU. The demulsability of theoil with Water must be rapid. The hydrocarbon oil acts as a diluent andalso minimizes the thermal decomposition of the lubricity agents, i.e.the fatty acid esters and fatty alcohols, during rolling. It has beenfound that with less than about 35% by weight hydrocarbon oil in thenonaqueous fraction, the lubricity agents tend to thermally decomposeduring rolling, causing a severe smut formation. Preferably, the lighthydrocarbon oil is between about 45% and 90% by weight of the nonaqueousfraction. Suitable hydrocarbon oils include Texaco 420-300 oil, HumbleOil Companys SOmentor 50 and Phillips Petroleum Companys Soltrol 250,which have the following typical properties:

TABLE I Humble Phillips Texaco Somen- Soltroll 420300 for 50 250Gravity, API at 60 F 37. l 42. 4 Specific gravity 60/60. 0. 84 0. 812 0.812 Viscosity, SSU at. 100 41. 8 50. 7 44. 0 Flash point, COG, F 280 230260 Four point, F +10 70 Naphthene carbon 33.3 Paraffin carbon 60. 3 83.3

3 alcohol typically contains about 1% C10 alcohol, 65% C12 alcohol, 24%C14 alcohol and about 10% C16 alcohol.

The emulsion also contains from to 50%, preferably 5 to 35%, by weightof the oil phase of a lower alkyl ester of a fatty acid, having from to20 carbon atoms. The lower alkyl group contains from 1 to 5 carbonatoms. Suitable esters include the methyl, propyl, isopropyl, butyl,isobutyl and pentyl esters of capric, lauric, myristic, palmitic,stearic, oleic and linoleic acids. The commercially available esters arealso usually mixtures of esters of various long chain fatty acids. Ofthe lubricity agents described above, lauryl alcohol and butyl stearatehave been found particularly useful.

The fatty alcohols in the oil-in-water emulsion of the present inventionare particularly suitable for cold rolling light metal products becauseof their superior (to the fatty acids, fatty acid esters, and fattyoils) load bearing or lubrication properties and their thermal stabilitywhen diluted in a light hydrocarbon base oil. The combination of thefatty alcohol with a fatty acid ester has a synergistic effect in thatit provides for better rolling characteristics and metal surface qualitythan the alcohol alone at equivalent concentrations and it also improvesthe thermal stability of both lubricity agents. Moreover, theutilization of both the fatty alcohol and fatty acid ester renders thebalance of the emulsifier or emulsifiers with the rest of theconstituents in the emulsion considerably less critical.

Essential to the present invention is the inclusion of an emulsifierwhich is soluble in the base oil and lubricity agents of the presentinvention but substantially insoluble in water. The emulsifier may bedispersible in water, however. One function of the oil-solubleemulsifier is to insure a substantially water-free layer of lubricant onthe sheet material during rolling. Sufficient amounts of the oil-solubleemulsifier are used to provide an oil-in-water emulsion in which themajority of the volume of the oil fraction is composed of oil globulesfrom about 2 to about 10 microns in diameter, which will remain stablefor at least minutes upon standing. In terms of the art, theoil-in-water emulsion of the present invention is termed a looseemulsion in that the emulsion in the quiescent state tends to separatesome free oil or break down in about an hour after emulsification. Tightemulsions generally are emulsions which have the majority of the oilfraction volume composed of globules less than 2 microns and which tendto be stable for days, weeks, and in some cases, months afteremulsification. Although termed loose, the emulsion of the presentinvention has little or no tendency to break down during rolling. Theoil phase does preferentially align itself adjacent to the workpiece,and the mill rolls due to the natural attraction thereto of the polarportions of the faty acid ester and fatty alcohol molecules. This,however, is not considered as an emulsion breakdown as it is understoodin the art.

To maintain the loose emulsion of the present invention, the level ofthe oil-soluble emulsifier is kept between 0.05 and 1.0%, preferablybetween 0.1 and 0.5%, by weight of the oil fraction. Suitableemulsifiers include the alkylaryl polyethyleneoxy andalkylpolyethyleneoxy phosphoric acid monoesters such as Antara LM-400and Antara LM-ZOO (GAF Corp.) and the glycerol monoesters of unsaturatedhydroxylated fatty acids such as Surfactol 13 (Baker Castor Oil Co.)which is glycerol monoricinoleate.

Preferably, the oil fraction of the present invention also contains anoil-insoluble nonionic emulsifier which is slightly soluble in water orat least dispersible in water. The function of the oil-insolubleemulsifier, among others, is to alfect a rapid and complete displacementof water on the workpiece, thus permitting deposition of a thin layer ofthe oil fraction. This water removing function is critical when theworkpiece entering the mill has water on the surface thereof.Apparently, due to the high moisture content of the atomspheresurrounding the entry side of the mill, a thin layer of moisturecondenses on the sheet which, if not displaced with oil, will causewater stain. The exact mechanism of removing water by the oil-insolubleemulsifier is presently not well understood. However, it has been foundthat both of the oil-soluble and oil-insoluble emulsifiers must bepresent to affect the deposition of a dry oil film on the metal beingrolled. The oil-insoluble emulsifier must be maintained between about0.05 and 1.0% by weight, preferably between 0.1 and 0.5% of thenonaqueous fraction. For substantially improved results the weight ratioof the oil-soluble emulsifier to oil-insoluble emulsifier should bemaintained between 1:1 and 1:10. Suitable nonionic emulsifiiers includepolyglycol esters of long chain fatty acids having been 10 and 20 carbonatoms, polyoxyalkylene ethers of long chain alkanes and ethoxylatedcastor oils. Examples of suitable nonionic emulsifiers are Brij 76 andBrij 92 produced by the Atlas Chemical Industries, Inc., which arerespectively a polyoxyethylene stearyl ether and polyoxyethylene oleylether; Unisol 4-0, produced by the Universal Chemicals Corp., which is apolyglycol ester of oleic acid, Surfactol 380, Surfactol 365 andSurfactol 318, produced by the Baker Castor Oil Co., which areethoxylated castor oils.

The need for the water-soluble emulsifier can be minimized bymaintaining the metal surface of the entry side of the mill at atemperature above the dew point of the atmosphere to preventcondensation. However, this is not desirable because an additionalheating step would be introduced into the process lines.

Although the above emulsifiers are termed oil-insoluble and oil-soluble,the combination of the two emulsifiers in the emulsion provides for anoil component concentration of between 300 and 1000 p.p.m. in the waterphase.

It has also been found that the amount of inorganic alkali metal salt inthe aqueous portion of the emulsion significantly affects thelubrication properties of the emulsion. A lithium, potassium and sodiumsalt concentration between about 10 and 400 p.p.m. provides for asubstantial increase in reduction per pass-e. g. increases up to 50% ormore with the common alloys. Suitable alkali metal salts include thechloride, fluoride, bromide, iodide and sulfate salts of lithium,potassium and sodium. Particularly effective and readily available aresodium sulfate and sodium chloride.

The emulsion of the present invention can be prepared by first mixingthe base oil, lubricity agents and one or more emulsifiers into a neatoil and then mixing the neat oil with water to form the emulsion. Thealkali metal salt, if used, can be mixed with the water in anyconvenient manner. Mechanical as well as sonic devices can be employedto mix the neat oil and water to form the oil-inwater emulsion.

The workpiece to be rolled as well as the mill rolls are flooded withthe emulsion as the workpiece enters the rolls. Preferably, the emulsionis removed from the sheet after rolling by suitable means such asmechanical wipers, air blasts, vacuum devices or combinations thereof.The emulsion tends to form water stain if not removed from the sheetbefore the sheet is coiled. However, a thin, dry oil film remains on thesheet after the emulsion is removed, which has no detrimental effects onthe surface characteristics of the metal.

The operating temperature of the emulsion should be maintained betweenabout 70 and 130 F., preferably between about and F. Below 70 theemulsion tends to invert, i.e., change to a Water-in-oil emulsion, andabove F. it tends to be unstable and breaks down to separate water andoil phases. Both of these phenomena are detrimental to the lubricitycharacteristics of the emulsion. During rolling, the emulsion becomesdirty due to the pickup of the metallic particles, decompositionproducts and other contaminants, which should be removed With somedegree of regularity due to their detrimental eifect on the surfacecharacteristics of the metal and rolling efficiency. The oil-in-wateremulsion is extremely difficult to :filter because of the relative sizeof the oil globules to the metal particles. It has been found that byheating the emulsion up to about 150, e.g. between 140 and 190 F., theemulsion can be easily separated into separate Water and oil phases bysuitable means such as by centrifuging. The oil phase, which containssubstantially all of the contaminant, can be filtered by a suitablefiltering means. The emulsion then is reconstituted and recycled forrolling. If necessary, additions can be made to the oil phase at thistime to maintain emulsion functionality. Over a period of time, the pHof the aqueous phase shifts toward the alkaline side, whichdetrimentally affects the lubricity characteristics of the emulsion.However, the pH is easily adjusted by suitable acidifying agents suchassulfuric acid. The buildup of metallic oxide particles on the rollsurface and the embedding of the particles into the surface of theworkpiece are minimized by the present emulsion.

To minimize oxidation of the lubricity agents, particularly those lefton the sheet after rolling, antioxidants such as 2,6 ditertiary butyl-4methyl phenol, commonly termed butylated hydroxytoluene (BHT) in amountsfrom 0.05 to about 0.50% by weight of the oil fraction are added to theoil phase before emulsification.

The following examples are given to further illustrate the invention.

by weight of at least one fatty alcohol selected from the groupconsisting of fatty alcohols having from 10 to 20 carbon atoms, from 5to 50% by Weight of at least one alkyl ester of a fatty acid selectedfrom the group consisting of fatty acids having from 10 to 20 carbonatoms, said alkyl portion having from 1 to 5 carbon atoms, and fromabout 0.05 to 1.0% of a substantially water-insoluble, oil-solubleemulsifier.

2. The neat oil of claim 1 containing from 5 to by weight of fattyalcohol and from 5 to 35% by weight of fatty acid ester.

3. The neat oil of claim 1 containing at least one waterinsoluble,oil-soluble emulsifier selected from the group consisting of alkylarylpolyoxyethylene phosphoric acid monoester, alkylpolyoxyethylenephosphoric acid monoester and glycerol monoricinoleate.

4. The neat oil of claim 1 containing from 0.05 to 1.0% of asubstantially oil-insoluble emulsifier.

5. The neat oil of claim 4 containing at least one oilinsolubleemulsifier selected from the group consisting of polyglycol esters offatty acids having from 10 to 20 carbon atoms, polyoxyethylene ethers oflong chain alkanes having from 10 to 20 carbon atoms and ethoxylatedcastor oils.

6. The neat oil of claim 1 containing lauryl alcohol and butyl stearate.

TABLE II.EMULSION COMPOSITION Neat oil percent Example 0f emulsi- NumberBase oil Lubricity agents Emulsifiers fiiers Water Butyl stearate 25%,lauryl alcohol, 25% LM-400, 0.14%; 4-0, 0.40% 1O Deionized, 2 .doLM-400, 0.11%; 4-0, 0.42% 10 D 3. Humble 3190, 49.6% ..do LM-400, 0.10%;4 0, 0.22% 10 Do, 4 Humble 3190, 47% utyl stearate, 23.9%; laurylalcohol, 23.9%-... LM400, 1.31%; 4-0, 3.86% 10 D0, 5 Humble 3190, 79.7%Butyl stearate, 10%; lauryl alcohol, 10% Surfactol13, 0.06%; Brij 76,0.24%. 10 Do. 6..-. Humble 3190, 69.7%... Butyl stearate, 25%; laurylalcohol, 5% Surfactol13, 0.05% Brij 92, 0.25% 10 Do.

7 Somentor 50, 50%

TABLE III Initial Thick- Thick- Thickthlckness ness ness Example ness,1st 2nd 3rd Surface quality Number Alloy inch pass pass pass afterrolling 202A 0. 125 0. 060 0. 042 0. 026 Excellent. 2024 0. 125 0. 0590. 042 0. 025 D0. 2024 0. 125 0. 059 0. 042 0. 026 Do. 2024 0. 125 0.059 0. 042 0. 264 Grey cast due to water stain. 2024 0. 125 0. 060 0.042 0.029 Excellent. 2024 0. 125 0. 060 O. 043 0. 029 Do. 1145 0. 0140.003 0. 0014 Do.

Examples 1 through 6 were rolled on a 2-hi Schmitz mill with mill rolls13 x 36 inches. Example 7 was rolled on a 2-hi Schmitz mill with millrolls 10 x 23 inches. Example 4 was included to show the determintaleffect of an excess of emulsifiers.

To illustrate the effectiveness of an alkali metal salt level above 10p.p.m., a 250-pound coil of 3003 aluminum alloy was rolled using theemulsion composition of Example 2. The first half of the coil was rolledwith a reduction from 0.026 to 0.0158 inch (about a reduction). The lasthalf of the coil was rolled after 16.p.p.m. NaCl was added to theemulsion with a reduction in thickness of from 0.026 to 0.010 inch(about a 62% reduction). In both instances all other controllableconditions were kept constant. The surface conditions of both halves ofthe coil were excellent.

Other uses of the present invention have been contemplated. For example,by employing a more viscous base oil the present invention can be usedin the rolling of ferrous products.

It is obvious that various modifications can be made to the presentinvention without departing from the spirit of the invention and thescope of the appended claims.

What is claimed is:

1. A neat oil comprising from about 35 to 90% by weight of hydrocarbonbase oil, from about 5 to 7. An oil-in-water emulsion suitable for thecold rolling of light metals comprising an oil phase comprising from 35to by weight of hydrocarbon base oil, from about 5 to 50% by weight ofat least one fatty alcohol selected from the group consisting of fattyalcohols having from 10 to 20 carbon atoms, from 5 to 50% by weight ofat least one alkyl ester of a fatty acid selected from the groupconsisting of fatty acids having from 10 to 20 carbon atoms, said alkylportion having from 1 to 5 carbon atoms, and from about 0.05 to 1.0% ofa substantially water-insoluble, oil-soluble emulsifier.

8. The oil-in-water emulsion of claim 7 comprising an oil phasecontaining from 5 to 35 by weight of fatty alcohol and from 5 to 35% byweight of fatty acid ester.

9. The oil-in-water emulsion of claim 7 comprising an oil phasecontaining at least one water-insoluble, oil-soluble emulsifier selectedfrom the group consisting of alkylaryl polyoxyethylene phosphoric acidmonoester, alkylpolyoxyethylene phosphoric acid monoester and glycerolmonoricinoleate.

10. The oil-in-water emulsion of claim 7 comprising an oil phasecontaining from 0.05 to 1.0% of a substantially oil-insolubleemulsifier.

11. The oil-in-water emulsion of claim 10 comprising an oil phasecontaining at least one oil-insoluble emulsifier selected from the groupconsisting of polyglycol esters of fatty acids having from 10 to 20carbon atoms, polyoxyethylene ethers of long chain alkanes having from10 to 20 carbon atoms and ethoxylated castor oils.

12. The oil-in-water emulsion of claim 7 comprising from 3 to 20% byweight of an oil phase.

13. The oil-in-water emulsion of claim 7 comprising an aqueous phasecontaining from 10 to 400 parts per million of an inorganic alkali metalsalt selected from the group consisting of the fluoride, bromide, iodideand sulfate salts of lithium, potassium and sodium.

14. The oil-in-Water emulsion of claim 13 in which the inorganic alkalimetal salt is selected from the group consisting of sodium chloride andsodium sulfate.

15. The method of cold rolling light metals comprising applying to theinterface between the light metal and rolling surface an oil-in-wateremulsion containing an oil phase comprising from 35 to 90% by weight ofhydrocarbon base oil, from about to 50% by weight of at least one fattyalcohol selected from the group consisting of fatty alcohols having fromto 20 carbon atoms, from 5 to 50% by weight of at least one alkyl esterof a fatty acid selected from the group consisting of fatty acids havingfrom 10 to 20 carbon atoms, said alkyl portion having from 1 to 5 carbonatoms, and from about 0.05 to 1.0% of a substantially water-insoluble,oil-soluble emulsifier.

16. The method of claim 15 wherein the oil phase contains from 5 to 35%by weight of fatty alcohol and from 5 to 35% by weight of fatty acidester.

17. The method of claim 15 wherein the oil phase contains at least onewater-insoluble, oil-soluble emulsifier selected from the groupconsisting of alkylaryl polyoxyethylene phosphoric acid monoester,alkylpolyoxyethylene phosphoric acid monoester and glycerolinonoricinoleate.

18. The method of claim 15 wherein the oil phase contains from 0.05 to1.0% of a substantially oil-insoluble emulsifier.

19 The method of claim 18 wherein the oil phase contains at least oneoil-insoluble emulsifier selected from the group consisting ofpolyglycol esters of fatty acids having from 10 to 20 carbon atoms,polyoxyethylene ethers of long chain alkaues having from 10 to 20 carbonatoms and ethoxylated castor oils.

20. The method of claim 15 wherein the emulsion contains from 3 to 20%by Weight of an oil phase.

21. The oil-in-water emulsion of claim 7 in which a majority of the oilfraction is composed of oil globules from about 2 to about 10 microns indiameter.

22. The neat oil of claim 1 in which the base oil has a viscositybetween about 30 and 100 SSU.

23. The oil-in-water emulsion of claim 7 in which the base oil has aviscosity between about 30 and 100 SSU.

24. The method of claim 15 wherein the base oil has a viscosity ofbetween about 30 and 100 SSU.

25. The method of claim 15 wherein the aqueous phase contains from 10 to400 parts per million of an inorganic alkali metal salt selected fromthe group consisting of the fluoride, bromide, iodide and sulfate saltsof lithium, potassium and sodium.

26. The method of claim 15 wherein the majority of the oil fraction iscomposed of oil globules from about 2 to about 10 microns in diameter.

27. The neat oil of claim 1 wherein the neat oil contains from to byweight of hydrocarbon base oil.

28. The oil-in-water emulsion of claim 7 wherein the oil phase containsfrom 45 to 90% by weight of hydrocarbon base oil.

29. The method of claim 15 wherein the oil phase contains from 45 to 90%by weight of hydrocarbon base oil.

References Cited UNITED STATES PATENTS 3,496,104 2/1970 Shinada et a1252-495 X 2,964,472 12/1960 Blum 252-l8 3,409,551 11/1968 Treat 252-49.5X

3,629,112 12/1971 Gower et al 25249.5 X

FOREIGN PATENTS 1,173,631 12/1969 Great Britain.

PATRICK P. GARVIN, Primary Examiner W. H. CANNON, Assistant Examiner US.Cl. X.R.

